This invention relates generally to actuator mechanisms and more particularly to a compact, rapidly operating and economical arrangement of print wires and actuating mechanisms therefor in a wire matrix printer. The invention also relates to certain features of actuator mechanisms and has particular utility in the selective movement of workpieces such as the print wires, found in wire matrix printers.
Matrix printers of various designs have been known for many years. Typical printers generally related to this invention are disclosed in P. A. Brumbaugh et al. U.S. Pat. No. 3,672,482; A. S. Chou et al. U.S. Pat. No. 3,592,311; E. B. Finnegan U.S. Pat. No. 3,627,096; R. S. Bradshaw U.S. Pat. No. 3,217,640; W. Wockenfuss et al. U.S. Pat. No. 2,683,410; and K. A. Knutsen U.S. Pat. No. 2,869,455; all incorporated by reference hereinto. Moreover, a copending patent application in the name of J. L. DeBoo et al., Ser. No. 468,046, filed May 8, 1974 and assigned to the same assignee as the present invention, is related hereto and is also incorporated by reference herein. Specifically, the actuator mechanisms described and claimed herein are intended to be alternatives to the electromagnetic actuator mechanisms described in the last-named application. The actuator mechanisms of this invention and of J. L. DeBoo et. al. are intended to be interchangeable, one with the other, in a wire matrix printer.
In various ones of the prior art matrix printers, a column of vertically spaced print wires is usually mounted on a carriage and traversed across the surface of a recording medium or surface, such as paper. In a typical printer using a 5 .times. 7 dot matrix for printed characters, the vertical column of seven print wires travels across the recording medium surface, five-positions-(or printing steps)-to-the-complete-character. At each possible printing position, selected ones of the print wires (from zero to all seven) are actuated or "fired" to impact or drive a printing end thereof against both an inked ribbon (or other marking medium) and the recording medium in a printing pattern based on which wires are actuated. Also, the selected wires may otherwise mark the recording medium in any known fashion such as by punching holes therethrough.
This invention, then, seeks to improve such matrix printers (1) by providing a rapidly operating, very light, compact, inexpensive, easy to make print head and print wire assembly, particularly one with essentially straight print wires, and (2) by providing very small, efficient, compact, easy-to-assemble and extremely rapid actuating mechanisms for operating such print wires. The invention also concerns a new and improved actuator, having general utility in selectively moving workpieces, but especially useful in selectively reciprocating an array of closely spaced parallel workpieces, such as the print wires of a matrix printer.
This invention is also concerned with an improved actuator mechanism of the general class disclosed in W. J. Zenner U.S. Pat. No. 3,056,546 and G. Dirks, U.S. Pat. No. 2,976,801 both incorporated by reference hereinto.
The Zenner patent relates to a punch system, including a combination of spring reeds and electromagnets for operating the reeds, to selectively cock and fire the reeds and associated punch elements. The present invention relates to improved actuators of the Zenner type wherein potential energy is stored in a spring-like member, which improved actuators are small, compact, and low in electrical power consumption.
The present invention, moreover, is also concerned with improved magnetic actuator structures of the general class disclosed in the Dirks patent. The Dirks patent relates to a dot printing system which includes a plurality of print levers having printing surfaces thereon. The levers are continuously reciprocated at a point intermediate the ends of the levers. Both ends of each print lever are attracted and held by permanent magnets. One of the permanent magnets also includes an electrical coil which, when energized, neutralizes the magnetic flux thereof. The relative strengths of the permanent magnets are such that if a particular neutralizing coil is not energized, reciprocation of its associated lever effects movement of the print end of that lever away from its magnet to cause printing. If the coil is energized, reciprocation of the lever moves only the non-printing end of that print lever away from the magnet and printing does not occur. The present invention involves an improvement and simplification of Dirks type actuators by eliminating the continuous reciprocation and one permanent magnet and simplifying other structural elements.
Actuators of the Zenner type as well as other actuators, such as those of the Brumbaugh et al. and Chou et al. patents rely on converting the potential energy stored in a reed or leaf spring to kinetic energy of a print wire to effect printing. Accordingly, another object of this invention is to improve on that concept by using a torsion spring rather than a reed. Simply stated, a torsion spring presents two advantages over a leaf spring. First, in a torsion spring, the storage of potential energy is accompanied by a uniform deformation. This means that other factors (material, size) being roughly equal, the torsion spring is capable of storing more potential energy per maximum stress more efficiently and in a more compact manner with potentially less movement than a leaf spring. Second, in a torsion spring, a mass to be driven thereby is essentially divorced from the spring. This is not true with a leaf spring wherein a significant part of the mass driven is the spring itself. The larger mass of a leaf spring renders it slower in driving an object, such as a print wire. Thus this invention uses these advantages or torsion springs to achieve a compact, efficient, high speed print head.
This invention further relates to the construction and geometry of actuator mechanisms which include pole pieces and armatures and to circuit operating principles for such actuator mechanisms and also relates to such actuator mechanisms which use a compact and low mass assembly of permanent magnets, pole pieces, armatures, and coils.